1. Field of the Invention
The present invention relates to an ink jet recording method for obtaining a high quality recorded matter.
2. Description of the Related Art
As an ink for ink jet recording there has heretofore been widely used a water-soluble liquid ink composition. It has been proposed that droplets of such a water-soluble liquid ink composition be allowed to penetrate readily the recording paper to enhance fixability. The layer of the water-soluble liquid ink composition formed on the recording paper has a thickness of from about 0 to 3 μm (When the thickness of the ink layer is 0 μm, the ink penetrates completely the recording paper). In the case where an ordinary recording paper allowing easy penetration of ink is used, bleeding occurs. Therefore, it is the status quo that the recording medium is limited to special coated paper.
In the case where printing is made on various plastic sheets, these sheets need to be subjected to special surface treatment to have an ink-receptive layer because the ink exhibits poor dryability (see, e.g., JP-A-4-359071, JP-A-4-359072, JP-A-2000-154344, JP-A-2001-26736).
A hot-melt type ink jet recoding method has been proposed involving the use of a hot-melt type ink composition made of a wax which stays solid at room temperature, etc. as an ink composition capable of providing a good recording quality regardless of the recording medium used. In the proposed hot-melt type ink jet recoding method, the hot-melt type ink composition is liquefied by heating or like means, and then given some energy so that it is ejected onto the recording medium where it is cooled and solidified while being attached thereto to form recorded dots (see, e.g., JP-A-2000-7968, JP-A-2000-7969, JP-A-2000-7970).
Further, a hot-melt type ink composition for ink jet recording aimed at the realization of so-called four-color system high quality full-color printing on the basis of definition of maximum chroma of various colors has been proposed (see, e.g., JP-A-2000-290555).
Moreover, a recording method which can be used for various recording media has been proposed as a recording method using an ink for ink jet recording method which is cured by ultraviolet rays or electron beam (see, e.g., JP-A-2000-136697).
Further, an ink jet printer process has been proposed which comprises reducing the period between the time of ejection of UV ink onto the recording medium and the time of curing and fixing by irradiation with ultraviolet rays to enhance the image color precision (see, e.g., JP-A-2003-127338).
In the art of color filter production, it has been proposed to control the ink layer thickness for the purpose of eliminating color unevenness (see, e.g., JP-A-2000-89023, JP-A-11-202115).
For an ink which is cured when irradiated with ultraviolet rays or electron beam, an ink jet printer has been proposed which comprises a light source mounted on the head carriage so that the recording medium is irradiated with light from the light source in the vicinity of the site hit by the ink droplet. However, this arrangement is disadvantageous in that the mounting of the light source adds to the weight of the head carriage, requiring the use of a complicated driving system for the head carriage for the purpose of withstanding the raised load and hence adding to the size and cost of the device.
On the other hand, in the case where the ink is cured when the recording medium passes through a light source portion provided downstream from the head carriage in the direction of conveyance of the recording medium, it takes from about several milliseconds to 1 second to cure and fix the ink which has been ejected from the recording head onto te recording medium by irradiation with light beam. Therefore, ink bleeding or fading (color unevenness) can occur under some working conditions such as characteristics of ink or recording medium or some atmospheric conditions such as temperature.
When the occurrence of bleeding or color unevenness is followed by the fixing of the ink, such a phenomenon forms an image as it is, causing image color precision drop or instability. In particular, when recording is made on a film or coated cardboard free of ink-absorbing layer, the resulting image quality depends also on between the surface energy of the film or coated cardboard and the ink, making the ink layer thickness different from the center to end of the image and hence causing color unevenness that deteriorates image quality.
The piezoelectric oscillator to be incorporated in the nozzles normally vary in displacement from unit to unit. Thus, the amount of ink to be ejected from the nozzles vary to cause color unevenness unless the displacement of these piezoelectric oscillators are made even.
In order to eliminate these problems, a countermeasure has been proposed which comprises varying the voltage applied to the piezoelectric oscillator in the nozzles to inhibit the dispersion of displacement of the piezoelectric oscillators. However, this approach involving the application of different driving signals to the piezoelectric oscillators is disadvantageous in that a driving signal producing circuit must be provided for each of the nozzles, adding to cost.
It is well known in the art that high quality printing requires the limitation of the optical density and color difference to specific range. However, in a recording method involving printing to an ink layer thickness of 15 μm or more and requiring much time to fix the ink, no countermeasure against color unevenness during ink jet printing is taken from the standpoint of control over physical properties of ink.